Acute ischemic stroke (AIS) usually occurs when an artery to the brain is occluded, preventing delivery of fresh oxygenated blood from the heart and lungs to the brain. These occlusions are typically caused by a thrombus or an embolus lodging in the artery and blocking the artery that feeds a territory of brain tissue. If an artery is blocked, ischemia follows, and brain cells may stop working. Furthermore, if the artery remains blocked for more than a few minutes, the brain cells may die, leading to permanent neurological deficit or death. Therefore, immediate treatment is critical.
Two principal therapies are employed for treating ischemic stroke: thrombolytic therapy and endovascular treatment. The most common treatment used to reestablish flow or re-perfuse the stroke territory is the use of intravenous (IV) thrombolytic therapy. The timeframe to enact thrombolytic therapy is within 3 hours of symptom onset for IV infusion (4.5 hours in selected patients) or within 6 hours for site-directed intra-arterial infusion. Instituting therapy at later times has no proven benefit and may expose the patient to greater risk of bleeding due to the thrombolytic effect. Endovascular treatment most commonly uses a set of tools to mechanically remove the embolus, with our without the use of thrombolytic therapy.
The gamut of endovascular treatments include mechanical embolectomy, which utilizes a retrievable structure, e.g., a coil-tipped retrievable stent (also known as a “Stentriever”), a woven wire stent, or a laser cut stent with struts that can be opened within a clot in the cerebral anatomy to engage the clot with the stent struts, create a channel in the emboli to restore a certain amount of blood flow, and to subsequently retrieve the retrievable structure by pulling it out of the anatomy, along with aspiration techniques. Other endovascular techniques to mechanically remove AIS-associated embolus include Manual Aspiration Thrombectomy (MAT) (also known as the “ADAPT” technique). MAT is an endovascular procedure where large bore catheters are inserted through the transfemoral artery and maneuvered through complex anatomy to the level of the embolus, which may be in the extracranial carotids, vertebral arteries, or intracranial arteries. Aspiration techniques may be used to remove the embolus through the large bore catheters. Another endovascular procedure is Stentriever-Mediated Manual Aspiration Thrombectomy (SMAT) (similar to the Stentriever-assisted “Solumbra” technique). SMAT, like MAT, involves accessing the embolus through the transfemoral artery. After access is achieved, however, a retrievable structure is utilized to pull the embolus back into a large bore catheter.